Manganese-regulated eg orbital occupancy coupled with anion dissociation enables efficient electrocatalytic oxidation of 5-hydroxymethylfurfural.

5-hydroxymethylfurfural oxidation reaction (HMFOR) offers a sustainable pathway for synthesizing the high-value platform chemical 2,5-furandicarboxylic acid (FDCA). Most prior studies have focused on morphological and electronic modulation, yet have overlooked the critical role of electronic spin configuration in governing surface reconstruction. Herein, manganese-doped cobalt carbonate hydroxide (Co2-xMnxCO3(OH)2) is fabricated via a facile cation-exchange strategy. X-ray photoelectron spectroscopy and physical property measurement system characterizations verify that Mn doping triggers intrinsic electron rearrangement within the 3d orbitals of Co active sites, which fundamentally modulates the orbital electron filling configuration of Co centers. Driven by such electronic structural evolution, partial high-spin Co2+ species in the electrocatalyst convert to an intermediate-spin state, reducing the proportion of high-spin Co2+ in the system. Density functional theory calculations further confirm the pronounced shift in eg orbital occupancy of Co2+, theoretically validating that Mn doping achieves precise spin-state regulation over Co sites. This electronic structure tuning remodels the local coordination environment, weakens metal‑oxygen bonds, and significantly accelerates lattice CO32- dissociation. The resultant Co centers with reduced eg occupancy preferentially adsorb OH- over HMF, facilitating rapid surface reconstruction at low applied potentials and generating highly selective active (Co3+/Co4+) species toward HMFOR. This work uncovers a spin-mediated surface reconstruction mechanism and provides a viable strategy for designing high-performance biomass electrocatalysts.